Spoj Blast Solution

Blast.java

package com.problems;

/**
 * @Author Mehdi Maick
 *
 */


import java.io.*;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Blast {
    static char[] A, B;
    static int k, a, b;
    static int[][] memo;

    static int f(int i, int j) {
        if (i <= 0)
            return j * k;
        if (j <= 0)
            return i * k;
        if (memo[i][j] != -1)
            return memo[i][j];
        int ans = 9999999;
        ans = Math.min(f(i - 1, j - 1) + Math.abs(A[i - 1] - B[j - 1]), ans);
        ans = Math.min(ans, f(i - 1, j) + k);
        ans = Math.min(ans, f(i, j - 1) + k);
        return memo[i][j] = ans;
    }


    public static void solve(FastReader fs, PrintWriter pw) {

        A = fs.next().toCharArray();
        B = fs.next().toCharArray();
        k = fs.nextInt();
        int m = B.length;
        int n = A.length;
        memo = new int[n + 2][m + 2];
        for (int i = 0; i <= n + 1; i++) {
            Arrays.fill(memo[i], -1);
        }

        pw.println(f(A.length, B.length));
    }

    public static int dpSolve(int m, int n) {
        int[][] dp = new int[m + 1][n + 1];
        for (int i = 1; i <= m; i++) {
            dp[i][0] = k * i;
        }
        for (int j = 1; j <= n; j++) {
            dp[0][j] = k * j;
        }
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                dp[i][j] = Math.min(Math.min(k + dp[i - 1][j], k + dp[i][j - 1]), dp[i - 1][j - 1]
                        + Math.abs(A[j - 1] - B[i - 1]));
            }
        }
        return dp[m][n];
    }

    public static void main(String[] args) throws Exception {
        FastReader fs = new FastReader(System.in);
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

        solve(fs, pw);

        fs.close();
        pw.close();
    }

    static class FastReader {

        BufferedReader reader;
        StringTokenizer st;

        FastReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
            st = null;
        }

        String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String line = reader.readLine();
                    if (line == null) {
                        return null;
                    }
                    st = new StringTokenizer(line);
                } catch (Exception e) {
                    throw new RuntimeException();
                }
            }
            return st.nextToken();
        }

        String nextLine() {
            String s = null;
            try {
                s = reader.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return s;
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        char nextChar() {
            return next().charAt(0);
        }

        int[] nextIntArray(int n) {
            int[] arr = new int[n];
            int i = 0;
            while (i < n) {
                arr[i++] = nextInt();
            }
            return arr;
        }

        long[] nextLongArray(int n) {
            long[] arr = new long[n];
            int i = 0;
            while (i < n) {
                arr[i++] = nextLong();
            }
            return arr;
        }

        int[] nextIntArrayOneBased(int n) {
            int[] arr = new int[n + 1];
            int i = 1;
            while (i <= n) {
                arr[i++] = nextInt();
            }
            return arr;
        }

        long[] nextLongArrayOneBased(int n) {
            long[] arr = new long[n + 1];
            int i = 1;
            while (i <= n) {
                arr[i++] = nextLong();
            }
            return arr;
        }

        void close() {
            try {
                reader.close();
            } catch (IOException e) {
                System.err.println("There's been an error trying closing the reader ");
                e.printStackTrace();
            }
        }
    }


}